The project is a continuation of a neurobiological investigation of the structure of ascending nonspecific systems. Experimental neuroanatomical studies will employ autoradiography, horseradish peroxidase histochemistry, and Golgi techniques. The cells of origin and areas of termination of first order projections of the brainstem reticular formation to the diencephalon will be determined, followed by studies of the origin and termination of second order reticular projections from the subthalamus and intralaminar and midline thalamus. Particular attention will be focused on thalamo-thalamic and thalamo-cortical connections. A variety of techniques and approaches will be used, and the results will be integrated in an attempt toward an overall understanding of the relationships of the brainstem reticular formation with the forebrain.